The Allied Kingdoms, also called the Four Kingdoms, were a coalition of Tion Cluster monarchies that joined the Confederacy of Independent Systems during the Clone Wars. Led by the dominant Kingdom of Cron, they also included the Kingdoms of Jaminere, Cadinth, and Barseg. In exchange for territories around the Tion Cluster, the kingdoms agreed to commit their military and economic strength to the Separatist war effort against the Galactic Republic.
As part of the terms signed between the Confederacy and the Four Kingdoms, the coalition pledged its fleets to aid the Confederate Navy. It was incomparable to the Separatist fleet and Republic Navy in numerical size but the royal armed forces were reputed for their professionalism and skill. Count Dooku and the Separatist Council believed that their military would come in useful as an elite vanguard force and for pacifying lightly-defended systems.
The Kingdom of Cron was the biggest contributor to the combined fleet, deploying 86 warships and more than 300,000 ground troops. Jaminere contributed 71 ships and 150,000 troops, Cadinth sent 53 ships and 110,000 men, while Barseg deployed 37 ships and 60,000 troops. The ground forces consisted of Military Household Guard, which were the best-trained and best-armed units in the Tion Cluster, and the most loyal to the monarchies. They were placed under the command of the most talented military commanders from each kingdom.
The pact between the Four Kingdoms and the Confederacy was sealed in 21 BBY, when Count Dooku approached House Thani and offered an alliance. The various states of the Tion Cluster had lost much territory and power over the centuries under the Republic, and House Thani saw this as an opportunity to regain some of what was lost.